Our long range objective is to determine the three-dimensional structures of biologically and medically relevant proteins of the vascular system. These proteins are involved in the transport and recycling of vital raw materials in the body. X-ray crystallographic techniques will be applied to the hemoglobin-haptoglobin complex. The structure of this molecule will show the interaction sites of the two proteins and any modifications in the conformation of the hemoglobin molecule. It may help to explain the elevated haptoglobin levels in heart disorders and cancers. Ceruloplasmin, the copper binding protein in serum, will also be studied crystallographically. The variety of copper-protein interactions and sites of oxidase activity should be elucidated by examination of this structure. The myeloma protein, IgG Garcia, will be crystallized and studied so that the structural basis for the strong interaction between riboflavin and this molecule can be understood. This molecule may prove to be a good model for the antigen-antibody interaction. An automated system for interpreting electron density maps of proteins is being developed using basic pattern recognition methods and fundamental properties of protein structure. Main chain coordinates have been derived and attention will now be focused on building side chains, improving the accuracy of the coordinates, and application of the methods to new protein electron density maps. Objective criteria for recognizing secondary structure in proteins will be used to study the interactions between secondary structure elements and the distribution of amino acid side chains in these elements.